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TitreGeological investigations of the Cat Creek area in the Neoarchean Bird River greenstone belt, southeastern Manitoba (part of NTS 52L12): new insights into PGE-Ni-Cu-Cr mineralization
AuteurYang, X M; Gilbert, H P; Houlé, M G
SourceReport of Activities 2012; Manitoba Geological Survey, Geoscientific Paper, 2012 p. 32-53
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20140521
ÉditeurCommission géologique du Canada
Mediapapier; numérique; en ligne
SNRC52L/12; 52L/11
Lat/Long OENS -95.7167 -95.2333 50.6833 50.3833
Sujetsroches vertes; tonalites; granodiorites; roches volcaniques mafiques; roches volcaniques felsiques; ensembles volcaniques; volcanoclastique; lopolites; dépôts de brèches; roches métavolcaniques ultramafiques; géochimie; géochronologie; pétrologie ignée et métamorphique
Illustrationslocation maps; geological maps; photographs; microphotographs; tables; graphs; ternary diagrams
ProgrammeÉtude des gîtes magmatiques de Ni-Cu-EPG, Initiative géoscientifique ciblée (IGC-4)
Résumé(Sommaire disponible en anglais seulement)
The Cat Creek area in the northern arm of the Bird River greenstone belt is situated approximately 145 km northeast of Winnipeg in southeastern Manitoba. The study area is underlain by a suite of typical greenstone assemblages within a continental-margin setting adjacent to the Mesoarchean Maskwa Lake Batholith. The rock assemblages consist of a tonalite-trondhjemite-granodiorite suite; supracrustal rocks that include mafic to felsic volcanic and synvolcanic intrusive rocks, and epiclastic and minor volcaniclastic rocks; the Mayville mafic-ultra-mafic layered intrusion; and late peraluminous granitoid rocks and related pegmatites. The Mayville intrusion consists of an east-trending lopolith approximately 10.5 km in length and up to 1.5 km in width. The intrusion is emplaced in a mid-ocean-ridge basalt (MORB) sequence to the south and west and is in structural contact with granitoid rocks to the east. To the north, the Mayville intrusion is emplaced in metasedimentary and intercalated volcaniclastic rocks, and is locally structurally juxtaposed against granitoid rocks. Although the Mayville intrusion has recently been the focus of ongoing mineral exploration because it hosts a significant amount of platinum group element (PGE)-Ni-Cu-Cr mineralization, some key metallogenic questions remain to be answered.
This report presents the preliminary results of geological mapping conducted at a scale of 1:12 500 by the Manitoba Geological Survey in 2012, together with new petrological, lithogeochemical and geochronological data acquired within the last year. Twelve map units have been identified in the Cat Creek area. The mapping and geochemical study suggest that the MORB-type basalts and related intrusive rocks, as well as the Mayville intrusion, may have been emplaced in an extensional back-arc environment characterized by a relatively thin crust (~21 km) and a continental-margin setting. The present geological map data indicate that the Neoarchean Mayville intrusion (U-Pb zircon age of 2743 Ma) consists dominantly of anorthositic gabbro, gabbroic anorthosite and anorthosite, with subordinate melagabbro and pyroxenite at the base and gabbro at the top. This intrusion is similar to Archean anorthosite complexes elsewhere, and can be subdivided into a lower heterolithic breccia zone and an upper anorthosite to leucogabbro zone. The geochemical signature of the Mayville intrusion suggests the parental magma(s) was an alumina-enriched tholeiitic type that may have been derived from a high degree of partial melting of the subcontinental lithospheric mantle; it may have experienced assimilation and fractional crystallization during its emplacement within the supracrustal rock succession. An early sulphide saturation event triggered by crustal contamination and/or introduced external sulphur is likely to have generated magmatic sulphide Ni-Cu-PGE mineralization at the base of the intrusion. The injection of a new batch(s) of a mafic-ultramafic melt may have resulted in PGE and chromite mineralization at transitional zones between various phases within the intrusion. In addition, calcic anorthosite in the Mayville intrusion may represent a potential source for the manufacture of aluminum-bearing chemicals.